Optimal Selection of Operating Conditions for an Oxygen Delignification Tower, 2002 International Pulp Bleaching Conference Proceedings

Sylvain Gendron, Jean Bouchard, and Richard Berry

Oxygen-based radicals have antagonistic effects on pulp: while they render lignin soluble, they also cause the cellulose chains to break. The rate of both effects is a function of the operating conditions. The selection of optimal conditions then consists of providing an acceptable balance between the two effects. Furthermore, significant costs may be associated with one or more of the process conditions, and can therefore influence the optimal solution. The key to the problem lies in properly defining an optimization objective function which can integrate all the relevant information. In this report, we develop a dynamic model for an oxygen delignification tower. It includes an empirical model of lignin removal and a first-principles model of cellulose degradation. Using this model, we determine the optimal conditions for operating the tower under alternative objective functions. The report provides the methodology and the algorithms, and, with a number of examples, shows that the objective functions can be easily optimized with a commercial spreadsheet program.